Question

A train passes an observer with an initial velocity u m/s standing on a platform. the first carriage of the train passes the observer ny a time 1 second and the second by a time 2 second.the length of each carriage is 12m

Answer 1

Let speed of train is u at the front of first compartment and v at the end of first and front of second compartment

let a be the acceleration

as 1 compartment takes 2 sec to cross the observer apply 1 eq of motion

v=u+2a [eq 1]

apply 2 eq of motion

15=2u+2a [eq 2]

 

now 2 compart takes 2.5 sct to cross the observer

apply 2 eq of motion

15=2.5v+3.125a  [eq 3]

 

solving the above 3 eq we get

u=147/18  a= -6/9